The expansion rate of the universe appears to vary from place to place, a new study reports. This finding, if confirmed, would force astronomers to reassess just how well they understand the cosmos.

"One of the pillars of cosmology — the study of the history and fate of the entire universe — is that the universe is 'isotropic,' meaning the same in all directions," study lead author Konstantinos Migkas, of the University of Bonn in Germany, said in a statement. "Our work shows there may be cracks in that pillar."

The universe has been expanding continuously for more than 13.8 billion years, ever since the Big Bang — and at an accelerating rate, thanks to a mysterious force called dark energy. Equations based on Einstein's general theory of relativity suggest that this expansion is isotropic on large spatial scales, Migkas wrote Tuesday (April 7) in a blog post about the new study.

Observations of the cosmic microwave background (CMB), the universe-pervading radiation left over from the Big Bang, support this notion, he added: "The CMB seems to be isotropic, and cosmologists extrapolate this property of the very early universe to our current epoch, nearly 14 billion years later."

But it's unclear how valid this extrapolation is, he stressed, noting that dark energy has been the dominant factor in the universe's evolution over the last 4 billion years or so. Dark energy's "baffling nature has not yet allowed astrophysicists to understand it properly," Migkas wrote. "Therefore, assuming it to be isotropic is almost a leap of faith for now. This highlights the urgent need to investigate if today's universe is isotropic or not."